With the development of electronic products, consumers have a higher and higher requirement for color gamut, and therefore the high color gamut design has become an important direction for the design of electronic products. In the high color gamut product design, the current mainstream approach to achieve high color gamut conversion is by using a quantum dot diaphragm. This kind of diaphragm can achieve high-efficiency color gamut conversion. However, cutting of the diaphragm usually renders an area of about 1 mm of the cutting area useless. For mobile products with narrow frames, a useless area resulted from the cutting may cause the quantum dot diaphragm not to be better applied to the products. In view of the above problems, it is desirable in the art to get rid of the defect that a useless area can be resulted from cutting of the diaphragm, so that the diaphragm can achieve better color gamut conversion so as to solve problems in the prior art.